Earth moving machines, for example dozers, motor graders, and wheel loaders, can have a front-mounted tool for pushing or carrying material. Some applications of these machines benefit from the tool being pitched forward or rearward about a horizontal axis that is generally perpendicular to a travel direction. Historically, the pitch angle of a machine tool was manually adjusted by way of a turnbuckle link that extended between a frame of the machine and an upper edge of the tool, in general alignment with the travel direction. In particular, shortening of the turnbuckle link generally resulted in rearward pitching of the tool, while lengthening of the turnbuckle link generally resulted in forward pitching of the tool.
While the turnbuckle link may have been suitable for some situations, it could also be problematic. For example, the turnbuckle link could self-adjust and/or rock back-and-forth when exposed to extreme vibrations, causing the pitch of the tool to move away from a desired angle. The turnbuckle link was also expensive and prone to damage under high loads. Further, because of the variable nature of the turnbuckle link, it may have been difficult to attain a consistent pitch angle of the tool between uses of the machine.
An alternative manual pitch adjustment assembly is disclosed in U.S. Pat. No. 5,853,051 of Buchanan et al. that issued on Dec. 29, 1998 (the '051 patent). Specifically, the '051 patent discloses a top link assembly for a construction machine that is used to adjust the pitch angle of a blade. The top link assembly includes a first adjustment plate connected to a top edge of the blade, and a second adjustment plate connected to a frame riser of the construction machine. Slots are formed within each of the adjustment plates. The top link assembly also includes spacer plates located at opposing sides of the adjustment plates that extend from the slots of the first adjustment plate to the slots of the second adjustment plate. Fasteners pass through holes in the spacer plates and the slots in the adjustment plates to engage corresponding nuts, such that tightening of the nuts causes the spacer plates to sandwich the adjustment plates therebetween and fix the pitch angle of the blade. With this configuration, loosening of the nuts and repositioning of the fasteners along a length of the slots results in a change of the pitch angle.
Although the top link assembly of the '051 patent may provide for a lower cost and/or reliable way to adjust the pitch angle of a work tool, it may still be less than optimal. In particular, the fasteners used to fix the pitch angle of the top link assembly may be exposed to high shear loads. In this configuration, the fasteners may need to be specially hardened to resist the shear loads without failure, which could be costly. In addition, it may be possible for the spacer plates to slide relative to the adjustment plates and thereby inadvertently adjust the pitch angle of the tool, if the fasteners are not properly tightened.
The pitch adjustment assembly of the present disclosure addresses one or more of the needs set forth above and/or other problems of the prior art.